On Tue, Feb 12, 2019 at 10:56:16AM +0800, Peter Xu wrote: > From: Andrea Arcangeli <[email protected]> > > This allows UFFDIO_COPY to map pages wrprotected. write protected please :) > > Signed-off-by: Andrea Arcangeli <[email protected]> > Signed-off-by: Peter Xu <[email protected]>
Except for two additional nits below Reviewed-by: Mike Rapoport <[email protected]> > --- > fs/userfaultfd.c | 5 +++-- > include/linux/userfaultfd_k.h | 2 +- > include/uapi/linux/userfaultfd.h | 11 +++++----- > mm/userfaultfd.c | 36 ++++++++++++++++++++++---------- > 4 files changed, 35 insertions(+), 19 deletions(-) > > diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c > index b397bc3b954d..3092885c9d2c 100644 > --- a/fs/userfaultfd.c > +++ b/fs/userfaultfd.c > @@ -1683,11 +1683,12 @@ static int userfaultfd_copy(struct userfaultfd_ctx > *ctx, > ret = -EINVAL; > if (uffdio_copy.src + uffdio_copy.len <= uffdio_copy.src) > goto out; > - if (uffdio_copy.mode & ~UFFDIO_COPY_MODE_DONTWAKE) > + if (uffdio_copy.mode & ~(UFFDIO_COPY_MODE_DONTWAKE|UFFDIO_COPY_MODE_WP)) > goto out; > if (mmget_not_zero(ctx->mm)) { > ret = mcopy_atomic(ctx->mm, uffdio_copy.dst, uffdio_copy.src, > - uffdio_copy.len, &ctx->mmap_changing); > + uffdio_copy.len, &ctx->mmap_changing, > + uffdio_copy.mode); > mmput(ctx->mm); > } else { > return -ESRCH; > diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h > index c6590c58ce28..765ce884cec0 100644 > --- a/include/linux/userfaultfd_k.h > +++ b/include/linux/userfaultfd_k.h > @@ -34,7 +34,7 @@ extern vm_fault_t handle_userfault(struct vm_fault *vmf, > unsigned long reason); > > extern ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long > dst_start, > unsigned long src_start, unsigned long len, > - bool *mmap_changing); > + bool *mmap_changing, __u64 mode); > extern ssize_t mfill_zeropage(struct mm_struct *dst_mm, > unsigned long dst_start, > unsigned long len, > diff --git a/include/uapi/linux/userfaultfd.h > b/include/uapi/linux/userfaultfd.h > index 48f1a7c2f1f0..297cb044c03f 100644 > --- a/include/uapi/linux/userfaultfd.h > +++ b/include/uapi/linux/userfaultfd.h > @@ -203,13 +203,14 @@ struct uffdio_copy { > __u64 dst; > __u64 src; > __u64 len; > +#define UFFDIO_COPY_MODE_DONTWAKE ((__u64)1<<0) > /* > - * There will be a wrprotection flag later that allows to map > - * pages wrprotected on the fly. And such a flag will be > - * available if the wrprotection ioctl are implemented for the > - * range according to the uffdio_register.ioctls. > + * UFFDIO_COPY_MODE_WP will map the page wrprotected on the > + * fly. UFFDIO_COPY_MODE_WP is available only if the > + * wrprotection ioctl are implemented for the range according ^ is > + * to the uffdio_register.ioctls. > */ > -#define UFFDIO_COPY_MODE_DONTWAKE ((__u64)1<<0) > +#define UFFDIO_COPY_MODE_WP ((__u64)1<<1) > __u64 mode; > > /* > diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c > index d59b5a73dfb3..73a208c5c1e7 100644 > --- a/mm/userfaultfd.c > +++ b/mm/userfaultfd.c > @@ -25,7 +25,8 @@ static int mcopy_atomic_pte(struct mm_struct *dst_mm, > struct vm_area_struct *dst_vma, > unsigned long dst_addr, > unsigned long src_addr, > - struct page **pagep) > + struct page **pagep, > + bool wp_copy) > { > struct mem_cgroup *memcg; > pte_t _dst_pte, *dst_pte; > @@ -71,9 +72,9 @@ static int mcopy_atomic_pte(struct mm_struct *dst_mm, > if (mem_cgroup_try_charge(page, dst_mm, GFP_KERNEL, &memcg, false)) > goto out_release; > > - _dst_pte = mk_pte(page, dst_vma->vm_page_prot); > - if (dst_vma->vm_flags & VM_WRITE) > - _dst_pte = pte_mkwrite(pte_mkdirty(_dst_pte)); > + _dst_pte = pte_mkdirty(mk_pte(page, dst_vma->vm_page_prot)); > + if (dst_vma->vm_flags & VM_WRITE && !wp_copy) > + _dst_pte = pte_mkwrite(_dst_pte); > > dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl); > if (dst_vma->vm_file) { > @@ -399,7 +400,8 @@ static __always_inline ssize_t mfill_atomic_pte(struct > mm_struct *dst_mm, > unsigned long dst_addr, > unsigned long src_addr, > struct page **page, > - bool zeropage) > + bool zeropage, > + bool wp_copy) > { > ssize_t err; > > @@ -416,11 +418,13 @@ static __always_inline ssize_t mfill_atomic_pte(struct > mm_struct *dst_mm, > if (!(dst_vma->vm_flags & VM_SHARED)) { > if (!zeropage) > err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma, > - dst_addr, src_addr, page); > + dst_addr, src_addr, page, > + wp_copy); > else > err = mfill_zeropage_pte(dst_mm, dst_pmd, > dst_vma, dst_addr); > } else { > + VM_WARN_ON(wp_copy); /* WP only available for anon */ > if (!zeropage) > err = shmem_mcopy_atomic_pte(dst_mm, dst_pmd, > dst_vma, dst_addr, > @@ -438,7 +442,8 @@ static __always_inline ssize_t __mcopy_atomic(struct > mm_struct *dst_mm, > unsigned long src_start, > unsigned long len, > bool zeropage, > - bool *mmap_changing) > + bool *mmap_changing, > + __u64 mode) > { > struct vm_area_struct *dst_vma; > ssize_t err; > @@ -446,6 +451,7 @@ static __always_inline ssize_t __mcopy_atomic(struct > mm_struct *dst_mm, > unsigned long src_addr, dst_addr; > long copied; > struct page *page; > + bool wp_copy; > > /*> * Sanitize the command parameters: > @@ -502,6 +508,14 @@ static __always_inline ssize_t __mcopy_atomic(struct > mm_struct *dst_mm, > dst_vma->vm_flags & VM_SHARED)) > goto out_unlock; > > + /* > + * validate 'mode' now that we know the dst_vma: don't allow > + * a wrprotect copy if the userfaultfd didn't register as WP. > + */ > + wp_copy = mode & UFFDIO_COPY_MODE_WP; > + if (wp_copy && !(dst_vma->vm_flags & VM_UFFD_WP)) > + goto out_unlock; > + > /* > * If this is a HUGETLB vma, pass off to appropriate routine > */ I think for hugetlb we should return an error if wp_copy==true. It might be worth adding wp_copy parameter to __mcopy_atomic_hugetlb() in advance and return the error from there, in a hope it will also support UFFD_WP some day :) > @@ -557,7 +571,7 @@ static __always_inline ssize_t __mcopy_atomic(struct > mm_struct *dst_mm, > BUG_ON(pmd_trans_huge(*dst_pmd)); > > err = mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr, > - src_addr, &page, zeropage); > + src_addr, &page, zeropage, wp_copy); > cond_resched(); > > if (unlikely(err == -ENOENT)) { > @@ -604,14 +618,14 @@ static __always_inline ssize_t __mcopy_atomic(struct > mm_struct *dst_mm, > > ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start, > unsigned long src_start, unsigned long len, > - bool *mmap_changing) > + bool *mmap_changing, __u64 mode) > { > return __mcopy_atomic(dst_mm, dst_start, src_start, len, false, > - mmap_changing); > + mmap_changing, mode); > } > > ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsigned long start, > unsigned long len, bool *mmap_changing) > { > - return __mcopy_atomic(dst_mm, start, 0, len, true, mmap_changing); > + return __mcopy_atomic(dst_mm, start, 0, len, true, mmap_changing, 0); > } > -- > 2.17.1 > -- Sincerely yours, Mike.
